What caused the most toxic algal bloom ever observed in Monterey Bay?

In spring 2015, the West Coast of North America experienced one of the most toxic algal blooms on record.
The bloom consisted of diatoms in the genus Pseudo-nitzschia, but researchers couldn’t tell why these algae had become so toxic. A new article shows that, at least in Monterey Bay, this bloom became particularly toxic because of an unusually low ratio of silicate to nitrate in the waters of the bay.

Some species of Pseudo-nitzschia diatoms produce a potent neurotoxin called domoic acid, which can cause seizures and death in mammals…